The FT100D draws about 20 amps maximum at a nominal 13.6 volts DC. I don't know what sort of battery you are using, but you need to make sure the battery and wiring will handle the 20 amp load.

I get the impression you are running the rig mobile. If you are, and the SWR is too high (>3:1), the radio will shut down its finals. The SWR needs to be under 2.5:1 and preferably lower. Instead of using the antenna, connect the rig to a dummy load and see if it transmits. If it does, the problem is not the radio.

If you can provide additional information, maybe I or one of the other hams can give you a better idea of the problem.

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